What time does to espresso

An espresso shot runs for about 25 to 30 seconds. Under 20 and it is under-extracted, sour and thin, lacking body. Over 40 and it is over-extracted, bitter and sharp, losing sweetness. The 10-second window between those two outcomes is where all espresso lives.

Beatrice is temperamental, and her mood affects the time. On a good day she is consistent. On a bad day, usually a humid one, she runs long and bitter or short and sour, and nothing I do to the grind fixes it until her mood passes.

This is why extraction time matters and why the pressure gauge matters and why the grind matters: because everything in espresso is about controlling what happens in those 25 to 30 seconds. The rest is theater.